G-Lader

It is essential that
you measure the boost pressure of your supercharger at the manifold
with an accurate boost gauge. Stock G-60's hit 9 lb of boost
(at sea level) just before the rev limiter cuts in. If you can't
get 9 lb, you may have a boost leak. I found one at the intercooler.
A hose clamp is great for round hoses, but not too good for oval
ones. I changed and sealed the oval hose on the intercooler (with
silicone seal) before reinstalling the hose clamp. Be careful
with silicone in the intake, though, as just a little bit ingested
by the engine will contaminate and destroy the oxygen sensor.

There is a special device
VW uses to find boost leaks. Chances are that you are no more
likely to have this than I was. Without this, you'll have to
investigate all connections between the supercharger and the
intake manifold (which, without the tool, is what I had to do).
Don't forget all vacuum lines coming out of the intake and going
to places like the power brake booster and the charcoal canister.
Check each hose, one-way check valve, and vacuum diaphragm with
your vacuum pump.

I found that sudden
pulses of pressure can damage these vacuum diaphragms. Popping
back (backfiring) while under boost ruined several of ours, including
the fuel pressure regulator, and vacuum modulator inside the
computer (available as a separate part for $90 from Bosch).

A common Corrado G-60
problem is low boost, and one surprisingly common reason is damaged
intercooler plumbing. We all think of plastic being more or less
impervious to acid, but in fact the plastic intercooler plumbing
of the Corrado often falls victim to acid damage from the battery.
Since the intercooler is in the driver's side front beneath the
battery, battery acid frequently damages the plastic plumbing.
This common source of a boost leak isn't that easy to find, hidden
away under the battery as it is, but there is a relatively simple
fix. Eurosport has some "replica" high-flow pulled-mandrel-bent
steel intercooler pipes for the Corrado that accurately replace
damaged stock units. Just to make sure, I recommend a battery
which won't cause acid damage, like the Optima, to make sure
the problem doesn't return.

If your oxygen sensor
fails and the system goes full rich, chances are you'll experience
some popping back as you struggle to keep the engine running.
If you can't find any boost leaks, yet you're way short on boost,
chances are the seal inside your G-Lader is gone.

This is not an uncommon
problem and is as likely to occur on a well maintained stock
G60 as one with an aftermarket pulley and chip. Since new G-Laders
cost over $2,000, you'd be wise to ship yours off for repair.
New Dimensions, here in the US, has a relationship with TEK,
the only factory authorized G-Lader rebuilder. It has the parts
(seals, bearings, and so on) and the expertise to rebuild your
G-charger. As icing on the cake, New Dimensions also offers several
stages of performance mods for the G-Laders, designed to make
more boost, and sooner. Essentially porting and polishing, these
performance mods make a significant difference in performance
and are the real secret to G-Lader performance.

Another likely suspect
(and extremely common source) for a small to moderate boost leak
is the idle stabilizer. To some extent, the leakage of this unit
can be at least minimized by turning the tiny Allen screw located
in one end. By blowing on the unit, it is possible to adjust
the Allen screw for minimum leakage. With age, these valves just
wear out.

The best solution, however,
is proposed by Neuspeed with it's latest HP kit or the check
valve called the Jiro Valve offered by Eurosport. Essentially,
the idle stabilizer is vented back into the intake, so the pressure
on each side of it is equal when under boost. Leakage doesn't
matter then. I fabricated such a part and found it to be an essential
mod.

Concerning the G-Lader
itself: There are specific rules you must follow to make yours
last. First, never let it over rev. The Firehawk race guys blew
six superchargers in one season, including one hand-made VW Motorsports
model. Just one incident of overreving (generally a missed shift
or an early downshift) virtually guaranteed a blown G-Charger.
They were often operating with the rev limiter defeated, but
even blew a few with the rev limiter operational. Since aftermarket
chips can up the rev limit to 7000 rpm, and aftermarket pulleys
substantially increase supercharger to engine gear ratio, it's
no secret that, at maximum rpm, the design limit of the G-Lader
is often dangerously close to being reached.

Fortunately the G-60
engine revs slow at high rpm (from the huge drag imposed by the
supercharger). This, along with the rev limiter, pretty much
protect you in the event of a missed shift, but offers no protection
should you downshift prematurely or into a much lower gear. Even
if you don't over rev your G-60, you must take further precautions
to make the G-charger last.

First is oil. the G-Lader
bearings are under great stress at 15,000 rpm and demand good,
fresh oil. I think synthetic is the only way to go in this car.
Mobil One, Amsoil, and Redline are my favorites. Owners who don't
change their oil regularly have reported losing the bearings
(and of course the rest of the G-Lader as well).

One of our project cars
lost two superchargers. The other is still on the original at
70,000 miles. The first car probably lost it's first G-Lader
due to running it without an air filter (but it sure runs fast
like that!) Dust and dirt are simply not tolerated. The second
car uses a good filter, like a K&N. Amsoil claimed to have
a foam filter that flows about as well as the K&N, but filters
small particles much better. I tried it, but the foam material
restricted air flow, the Amsoil filter robbed as much horsepower
as the Autothority chip added! Eurosport sells the ITG Pro-Filters,
which seem to offer the best of both worlds when it comes to
filtration and flow. More importantly, Eurosport has a mandrel-bent
inlet from the filter to the G-Lader inlet and a fabricated heat
shield to keep hot air out of the air inlet. It's an elegant
solution to at least part of the "more air flow" problem.